Swingmill Blade Maintenance and Running Costs

Part 5 of a 5-part series on what you need to know about swingmill blades

A swingmill has a single circular blade that pivots; it moves forward in a horizontal position to make the first cut, pivots to vertical at the end of the log, and then moves back to it’s starting position as it saws in vertical. Your dimensional board can now be removed from the log completely edged and square. The log remains completely still, so there’s no log turning, edging or resawing involved.

Swingmills are the sawmill of choice in the countries they originated from, and around most of the Pacific and Africa.  Petersons in New Zealand were the first in 1989, then Lucas in Australia started manufacturing around 1995. But swingmills are still in the ‘gaining popularity’ phase in many northern-hemisphere countries such as the US, Canada, and Europe, mostly because of lack of information. There are some great internet forums that share a wealth of knowledge on all types of sawmills, including swingmills. Try places like www.forestryforum.com and www.woodweb.com for owners who are more than happy to help you with feedback, maintenance and running costs on the swingmills they run.

Normal Wear of Tips

After a few weeks of serious milling, the tips will get thinner as you sharpen them down. A tip can be used down to about ¼ of it original thickness, or about 1.5mm or 3/64^th of an inch thick. Assuming you don’t hit any metal, a set of tips on a swingblade will last about 17,000 board feet, or 40 cubic metres of sawn timber. To get a blade fully retipped, you will pay anywhere from $30-$70 depending on your sawdoctor’s rates.

Hitting Metal

When you hit metal with a bandsaw, the blade is usually a write-off. Hence the requirement to have a couple boxes of spare bandsaw blades on hand at any one time. So that’s around $20 a pop plus your downtime changing blades in the middle of your job.

When you hit metal with a swingblade, you will usually chip 1-4 teeth. One or two missing teeth still leaves you 4-8 good ones that you can still finish the job with. In most cases you can carry on fine. Take the blade home with you at night, and replace the one or two damaged tips yourself with a retipping jig. Or, you can drop the blade into your sawdoctor.

Bottom line, invest in a good metal detector – they will save you money on ANY type of sawmill.

Re-tipping

Most swingblade manufacturers supply re-tipping jigs that will assist you in replacing tips in your own garage. You can purchase pre-shaped and pre-tinned tips (with solder and flux on them) to weld on yourself with a basic oxy-acetylene welding set. Basically you need to compare the cost of the jig and tips, versus the downtime getting your blades to a sawdoctor, especially if the nearest one is more than a couple hours away! Retipping costs will be anywhere from $4 for a DIY single tip to $70 for re-tipping and servicing an entire blade.

Re-Tensioning

Loss of tension is caused by forcing your blade through the cut when it’s out of adjustment, when it’s blunt/dull, or if it’s incorrectly spec’d. Tension also goes over time by good old hard work. A good blade can easily last through 2 sets of teeth, or around 34,000 board feet or 80 cubic meters of sawn timber before tensioning is required.

A good sawdoctor will retension your blade during a retip service, for very little extra, if any. You will need to tell your sawdoctor what rpm your blade is running at, and the tooth specifications (spec sheet usually supplied by the manufacturer). Modern sawdoctors will roll-tension your blade, where the blade is rotated while it’s being pressed by two bearings. You will see rings on your blade if it has been roll tensioned. This method distributes tension more effectively, but the old fashioned hammer-tension is still sufficient if carried out by a skilled sawdoctor. A tension service on its own can cost anywhere from $10 to $40.

Blade Maintenance Time & Costs Summary

Setting aside for the moment the arguments between bandsaws and swingmills regarding production rates and recovery rates, lets look at typical blade maintenance costs only. This is assuming both mills cut exactly the same amount of timber (1900bft or 4.5cubes) in an 8-hour day, and that neither hit metal. Here is a pretty comprehensive table that has been drawn up from data from two operators using the two different machines in the field. Typical blade maintenance costs and usage periods like these can also be found on the forums mentioned above.

Recommended Sawdoctors (Blade Maintenance Service Providers)

When you take your blade in for its first re-tipping, you will need to give your sawdoctor the manufacturer’s specification sheet which will show the correct tooth size and width required, and the hook and rake angles. When the blade comes back, compare it to the other one you have. Then take note of the blade’s performance on the mill, and give your sawdoctor some feedback. He might not get it perfect for you the first time ‘round, so he does need to know what to change to get it just right. And once you gain confidence in your sawdoctor, it would be great to recommend him to other swingblade mill owners.

Here are just some of the many sawdoctors that swingmill customers use for their blades, and whom they have referred to us as all-round good service providers. I’m sure there are many more, but at least this is somewhere to start!

There are 4 more sections of this article:
· Swingmill Blade Maintenance
· Re-Tipping & Sharpening
· Plate (Body), Gullets & Tensioning
· Blade Adjustments to Run True